1. Field of the Invention
The disclosed embodiments of the present invention relate to audio playback, and more particularly, to a method for synchronizing audio playback of a plurality of digital media renders (DMRs) and related digital media controller, digital media server, and digital audio media player.
2. Description of the Prior Art
An industrial standard of mutual connection and mutual adaption of products of distinct manufacturers for providing digital living to consumers is achieved by the Digital Living Network Alliance (DLNA). The DLNA specification is also employed by a home digital audio and video media playback system including a digital media controller (DMC), a digital media server (DMS), and a plurality of digital media renders (DMRs). However, in a case where the DMRs, the DMS and the DMC are connected via wireless means, the DMRs receive audio data from the DMS for audio playback by way of wireless connection. The advantages include the simplified wired configuration and improved flexibility for future equipment update. However, the disadvantage is that the wireless transmission has poorer stability when compared with the wired transmission. The DMRs may be asynchronous to each other apparently at the initial condition of the playback or during the playback as the system is subject to interference. The DMRs may also be gradually asynchronous to each other under a stable connection due to a slight difference between DMRs' oscillator frequencies. Therefore, how to control and synchronize a plurality of DMRs has become a significant concern in this field.
Regarding the conventional synchronization design of DMRs, an absolute timing concept is employed. Specifically, each DMR may have information with absolute timing to comply with. However, many systems, including the DLNA systems, do not offer information about absolute timing due to simplified system designs. As a result, the conventional synchronization design cannot be employed by these systems. Therefore, there is a need for an innovative design which can synchronize a plurality of DMRs.